Thermal type overload circuit breaker



Aug. 18, 1942. N. L. cAsE ETAL THERMAL TYPE OVERLOAD CIRCUIT BREAKER Filed June 26, 1940 ATTORNEYS Pmiaed Aug. 18, 1942 THERMAL ma ovaanoan cracurr BREAKER.

Noel L. Case and Edward E. McKeige, Girard, Pa., assignors to Louis Marx & Company, Inc., New York, N. Y a corporation of New York Application June 26, 1940, Serial No. 342,460 '1 Claims. '(01. zoo-11o) This invention relates to overload circuit breakers, particularly for toys such as toy railroads.

The primary object of the present invention is to generally improve overload circuit breakers,

particularly low voltage circuit breakers for electrically-operated toys such as toy railroads. A more particular object is to provide such a device which may also be used as a manuallyoperated circuit breaker, this being desirable for signalling or remote control purposes. Still another object is to so arrange the restoring button or control as to make it impossible to hold the circuit closed manually after it has been opened by a short circuit or similar overload.

Other objects of the invention are to provide a circuit breaker which is simple in construction, dependable in operation, compact in dimension, and low in manufacturing cost. A still further object of the invention is to so arrange the parts of the circuit breaker that they may be housed in the relatively slender upright part of a support for a lamp or like signal showing when the circuit breaker has opened.

To the accomplishment of the foregoing and other objects which will hereinafter appear, our invention consists in the circuit breaker elements and their relation one to the other as hereinafter are more particularly described in the specification and sought to be defined in the claims. The specification is accompanied by a drawing, in which:

Fig. l is a section taken in elevation through an overload circuit breaker embodying features of the invention;

Fig. 2 is a plan view thereof;

Fig. 3 is a perspective view showing the configuration of the thermostatic element;

Fig. 4 is a section through the circuit breaker with the contacts in closed condition;

Fig. 5 illustrates the operation of the push button as a manua1 circuit breaker;

Fig. 6 illustrates the relative location of the parts following a short circuit or overload Fig. 7 shows how the parts may be restored to working position, without manually closing the circuit;

Fig. 8 is a section taken in elevation through a modified form of the invention, and is taken approximately in the plane of the line 8-4 of Fig. 9 is a section through the mechanism taken in the plane of the line 8-! of Fig. 8;,

Fig. 10 is a bottom plan view of the modification;

Fig. 11 is a wiring diagram for the circuit breaker; and i Fig. 12 is explanatory of a detail.

Referring to the drawing, and more particularly to Fig. 4, the circuit breaker comprises insulatedly mounted front and back spring contacts i2 and Il which are normally closed at It, as is indicated in the drawing. The front contact I! is so shaped that it normally tends to spring toward the right or away from the contact ii to the open circuit position shown in Fig. 6. However, lt is normally held in the closed contact position by a sleeve l8 slidable on a pusher 20, the sleeve ll being held in the left-hand position shown in Fig. 4 by a detent 22. Detent 22 forms a part of the thermostatic element of the circuit breaker. Its configuration will be clear from inspection of Fig.'3 in which it will be seen that the thermostatic element comprises spaced legs 24 and 26 integrally connected at one end by the detent ledge 22. A generally U-shaped piece,- having the configuration shown in Fig. i2,

is stamped or punched from a sheet of laminated or thermostatic metal. The U-shaped piece is then bent at both ends to the shape shown in Fig. 3, the upwardly bent closed end 22 acting as the detent ledge, and the downwardly bent parts 2! acting as a convenient means for attachment to a suitable support such as the insulation wall ll in Fig. 4. I I

The detent normally assumes the upward position shown in Fig. 4, and thereby holds the sleeve II in the left-hand position shown, and so keeps the front contact I! closed against the rear contact l4.

'I'he laminations of different metals in the thermostatic element are such that overheating tends to cause the same to bend downwardly from the position shown in Fig. 4 to the position shown in Fig. 6. This releases the sleeve i8, whereupon the front contact I2 springs away from the rear contact ll, thus opening the circuit to be protected.

The thermostat and the contacts are preferably connected in series with one another and with the circuit to be protected. Thus, referring to Fig. 11, the step-down transformer 31 may be a typical toy transformer having its primary 3! connected to a household wiring outlet, and having its secondary 38 connected to the service rails 38 and third rail 40 of a toy railroad. The thermostatic detent 22, 24, 26 is connected in series with the contacts I2, I and both are arranged in series with the transformer circuit, as is clearly shown in the wiring diagram. Terminals t2 and M are preferably provided ior convenience, and a lamp d5 is preferably connected across terminals 62 and 16 or in parallel with the circuit breaker mechanism. In the event of an overload or short circuit, the current flowing through the thermostatic element becomes excessive and heats the same, whereupon the contacts i2, is are permitted to open. The lamp 56, which is normally extinguished because oi the low voltage across the circuit breaker mech= anism, is lighted when the circuit breaker opens,

thus warning of the condition to be corrected.

Reverting now to Fig. 6, the opening of the circult permits the thermostat to cool, and it thereupon moves upwardly from the solid line position 22 to the broken line position 22' where it rests against the sleeve it. To close the circuit breaker, it is merely necessary to depress the pusher or button 28, this having a diameter somewhat greater than the inside diameter of sleeve i8, and so moving the sleeve relative to detent 22 until the latter moves upwardly at the end of the sleeve, as is shown in Fig. 7.

In order to prevent the button 2b from being used to manually hold the circuit closed despite the existence of a short circuit, with-possible burning out of the transformer or other hazard,

the pusher is preferably arranged to move the it possible for detent 22 to engage and hold the sleeve iii, the pusher also pushes the rear contact i i toward the left, thus keeping the contacts open at id. The circuit is closed when the button 26 is released, for then the rear contact moves to the right and the parts assume the relation shown in Fig. 4. Note, however, that at this time the button has been released and,

therefore, if the short circuit still exists the ther mostat will again quickly heat and so release the front contact as is shown in Fig: 6.

With the construction shown the button 2&3 may be used as a manual means to momentarily break the circuit. This is useful in connection with certain types of toy trains which are ar= ranged to reverse or to perform some other op eration under remote control. Referring to Fig. 5 the parts are there shown in the same relation as in Fig. 4, except that the button 28 has been depressed. This causes the part td of the pusher to move the rear contact id away from the front contact i2, thereby opening the circuit, there be ing no change in the positions of the sleeve 88 and the detent 22.

While not essential, it is convenient tomake the pusher 26 in the form of a stepped cylinder made of insulated material. The endmost part 56 of smallest diameter is slldable in a hole in in sulation back plate 39. The part Ell ls'preferably slidable througha hole in the lower end of contact iii. The part $8 is of larger'dlameter than the hole and, therefore, controls the position of contact id. This part, however, passes through a larger hole in the lower end of contact 52, and does not control the position of contact i2. That is controlled instead by the sleeve it which is slidable on the part d8 of the pusher. The next step on the pusher is the part 52 (Fig.

4) which is somewhat larger than: the inside 7 daeasea diameter of sleeve 88, yet substantially smaller than the outside diameter of the sleeve. It is larger than the inside diameter in order to move the sleeve when the button is pushed, but it is smaller than the outside diameter in order to permit the detent 22 to engage the end of the sleeve when the button is pushed inwardly as shown in Fig. 7. This part 52 may have the same diameter as the button 28, and in such case a collar lid of still larger diameter is preferably provided to limit outward movement of the button as shown in Figs. 4 and 6.

The button is slidable in a hole through a metal wall 68. This is the end or connecting wall of a piece of sheet metal bent to U-shape, one of the sides of the U being shown at 52, and both sides being shown at e2, 84 in Fig. 2. The metal piece is secured to an insulation base 30 by suitable tongue and slot connections St.

Referring now to Figs. 1 and 2 of the drawing, the lamp it is received in a socket ill carried on a top it which may be made of a suitable plastic. Top l2 closes the upper end of a hollow sheet metal support M which is preferably made by bending a single piece of heavy gauge sheet metal to form four side walls connected at a suitable seam it (Fig. 2). These are carried on an upwardly dished sheet metal base i8 which in turn carries the binding posts t2 and 64. One of these may be grounded to the metal, but the other must be insulated. The upright support It is secured to base it by suitable tongue and slot connections, the tongues being bent beneath the base. The top it is secured to the walls M by tongue and slot connections but, in this case, it is preferable to secure the tongues in the plastic by pins (Fig. 1) instead of by bending the tongues. Lamp 86 is enclosed by a suitable globe tfi'which may, if desired, be made of a translucent plastic. r s

- The circuit breaker unit is secured within the upright housing id, as by means of screws 88 which pass through one wall of the housing and which are threadedly received in the front wall 6% of the sheet metal frame. Connections to the thermostat are made at the legs 28, while connections to the switch contacts 92 and it are made at their upper ends.

A modified housing iorthe invention is shown I is extended both upwardly and downwardly.

The upwardly extending part 92 is bent to horiaontal position at M and forms a support for lamp socket 98. The .downwardly extending part 99 is bent to horizontal position at we, and has mounted thereon suitable terminals such as the Fahnstock clips are and ltd (Fig. 10). One of these, in this case the clip m2, is secured directly on and grounded to the metal, while the other, in this case the clip lot, is insulatedly mounted. Screws we may be used to secure the plate Hill in the base part are of the housing iii]. The upper plate 96 iS suitably dimensioned to prevent side to side movement. The button 20 projects through a hole in the casing H0, and the latter is, oi. course, preferably made of a translucent plastic. It may, for example, be colored red, in which case it will glow with a red lamination when the lamp 46 is lighted, thus warning that the circuit breaker is open.

It is believed that the construction and operation, as well as the many advantages of our improved thermal type circuit breaker will be ap parent from the foregoing detailed description thereof, It will also be apparent that while we have shown and described the invention in several preferred forms, many changes and modiflcations may be made in the structures disclosed without departing from the spirit of the invenbe defined in the following in said pusher for engaging and moving the step,

a thermostat detent to normally hold the step in such position as to keep the contacts closed,

means connecting said thermostat and said contacts in series. with each other and with the line to be protected, the direction of movement of said thermostat being such that when overloaded and heated it bends away from the step and so permits opening of the contacts, the depression of said pusher restoring the step to proper position to again be engaged by the detent but at the same time moving the rear contact so that it is impossible to hold the contacts closed by means of the push-button, the slidable relation between the slidable step and the pusher affording outward movement of the pusher and the rear contact after the slidable step has been engaged by the detent.

2. An overload circuit breaker comprising a pair of collaterally arranged spring contacts tending to open, a pusher extending transversely of said contacts and having an exposed end acting as a push-button, said pusher having a part adapted to bear against and push the further contact away from the nearer contact, thereby opening the circuit whenever the push-button is pressed, a sleeve surrounding and slidable on said pusher, said sleeve bearing against and being adapted to control the position of the nearer contact, means on said pusher for engaging and moving the sleeve, a detent to normally hold the sleeve in such position as to keep the contacts closed, said detent being a thermostat cut to U-shaped configuration and disposed generally transversely of the contacts with the closed end of the U bent transversely of the legs to form a detent ledge for engaging the aforesaid sleeve and holding the contacts closed, means connecting said thermostat and said contacts in series with each other and with the line to be protected, the direction of movement of said thermostat being such that when overloaded and heated it bends away from the sleeve and so permits opening of thecontacts, the depression of said button restoring the sleeve to proper position to again be engaged by the detent ledge,'but at the same time moving the rear contact, whereby it is impossible to hold the contacts closed by means of the push-button, the slidable relation between the sleeve and the pusher affording outward movement of the pusher and the rear contact after the sleeve has been engaged by the detent;

3. An overload circuit breaker, particularly for toy railways, said circuit breaker comprising a pair of spring contacts tending to open, a pusher extending transversely of said contacts and having an exposed end acting as a push-button, said pusher being cylindrical and stepped in diameter, a small-diameter inner end passing through the further contact and through a guide wall whereby an intermediate-diameter portion is adapted to bear against and push-the further contact away from the nearer contact, thereby opening the circuit whenever the push-button is pressed, said intermediate-diameter portion passing through the nearer contact, a sleeve surrounding and axially slidable on said intermediate-diameter portion, said sleeve bearing against and being adapted tocontrol the position of the nearer contact, a large-diameter portion on said pusher for engaging and moving the sleeve, a thermostat detent to normally hold the sleeve in such position as to keep the contacts closed, means connecting said thermostat and said con tacts in series with each other and with the line to be protected, the direction of movement of said thermostat being such that when overloaded and heated it bends away from the sleeve and so permits opening of the contacts, the depression of said button restoring the sleeve to proper position to again be engaged by the detent, but at the same time moving the rear contact, whereby it is impossible to hold the contacts closed by means of the push-button, the slidable relation between the sleeve and the pusher affording outward movement of the pusher and the rear contact after the sleeve has been engaged by the detent.

4. An overload circuit breaker comprising a frame having spaced front and back walls, front and back spring contacts mounted insaid frame and extending in the direction of said front and back walls, said contacts normally tending to separate, an insulation pusher rod extending transversely of said contacts through said front and back walls, said pusher rod having a smalldiameter inner end portion passing through said back contact and said back wall, a medium-diameter intermediate portion passing through said front contact and abutting said back contact, a sleeve slidable on said intermediate portion and abutting said front contact, the next forward portion of said pusher'rod being of large diameter and the forward end of said pusher rod projecting through the front wall of the frame and acting as a push-button for said pusher rod, and a thermostatically controlled detent for engaging said sleeve to normally hold the contacts closed, the steps of said pusher rod being so related that depression of the push-button moves the back contact away from the front contact at the same time that it moves the sleeve into position for engagement by the detent.

5. An overload circuit breaker comprising a frame having spaced front and back walls, front and back spring contacts mounted in said frame and extending in the direction of said front and back walls, said contacts normally tending to separate, an insulation pusher rod extending transversely of said contacts through'said front and back walls, said pusher rod having a smalldiameter inner end portion passing through said back contact and said back wall; a mediumdiameter intermediate portion passing through said front contact and abutting said back contact, a sleeve slidable on said intermediate portion and abutting said front contact, the next forward portion of said pusher rod being of large diameter and the forward end of said pusher rod 4- encased.

sheet metal cut to U-shaped configuration and disposed transversely of the contacts in the direction of the pusher rod, theclosed end of the U- shaped thermostat being bent transversely of the legs to form a detent ledge for engaging the sleeve, the steps of said pusher rod being so related that depression of the push-button moves the back contact away from the front contact at the same time that it moves the sleeve into position for engagement by the detent.

6. An overload circuit breaker comprising a frame having spaced front and back walls, front and back spring contacts mounted in said frame and extending in the direction of said front and back walls, said contacts normally tending to separate, an insulation pusher rod extending transversely of said contacts through said front and back walls, said pusher rod having a smalldiameter inner end portion passing through said back contact and said back wall, a mediumdiameter intermediate portion passing through said front contact and abutting said back contact, a sleeve slidable on said intermediate portion and abutting said front contact, a largerdiameter step ahead of the sleeve, said step having a diameter larger than the inside of the sleeve in order to preventforward movement of the sleeve, but smaller than the outside of the sleeve so that the forward end of the sleeve may be used for engagement by a detent, the forward end of said pusher rod projecting through the front wall of, the frame and acting as a push-button or said pusher rod, and a thermostatically controlled detent for engaging said sleeve to normal- Ly hold the contacts closed, the steps of said pusher rod being so related that depression of the push-button moves the back contact away from the front contact at the same time that it moves the sleeve into position for engagement by the detent.

7; An overload circuit breaker comprising a frame having spaced front and back walls, front and back spring contacts mounted in said frame and extending in the direction of said front and back walls, said contacts normally tending to separate, an insulation pusher rod extending transversely of said contacts through said front and back walls, said pusher rod having a'smalldiameter inner end portion passing through said back contact and said back wall, a, medium-.

diameter intermediate portion passing through said front contact and abutting said back contact, a sleeve slidable on said intermediate portion and abutting said front contact, a largerdiasneter step ahead of the sleeve, said step having a diameter larger than the inside diameter of the sleeve in order to prevent forward movement of the sleeve, but smaller than the outside of the sleeve so that the forward end of the sleeve may be used for engagement by a detent, a stop portion of still larger diameter, the forward end of said pusher rod being smaller in diameter than the stop portion and projecting through a mating hole in the front wall of the frame and acting as a push-button for said pusher rod, the aforesaid stop portion limiting outward movement of the pusher rod, and a thermostatically controlled detent for engaging said sleeve to normally hold the contacts closed, the steps of said pusher rod being so related that depression of the push-button moves the back contact away from the front contact at the same time that it moves the sleeve into position for engagement by the detent.

. N0 L. CASE.

WW E. McKEIGE. 

